Science doesn't have beliefs it has theories. Those are two different things.

Belief in God for Christians is a sure thing. In their hearts and minds the know that God exists no matter what evidence you provide to the contrary.

A Theory is an idea about how something works. Everyone in science knows its not fact but a possibility.

So you see, if a Christian or other deity worshiper believed in the big bang theory they would know its a fact and without a doubt in their mind its proof. While science knows its just a possibility of creation and probably the best idea there is thus far.